The present invention relates to improvements in methods and apparatus for making rod-like streams of smokable materials, especially for making streams which consist of or contain natural tobacco, reconstituted tobacco and/or substitute tobacco and can be converted into the fillers of cigarettes or other rod-shaped smokers' products.
German Pat. No. 11 64 907 discloses a cigarette whose filler is formed with a centrally located longitudinally extending air channel. The cigarette is formed by inserting into the filler a stationary mandrel which serves to continuously admit into the surrounding portion of the filler a hardening agent in order to ensure that the axially extending channel remains intact upon extraction of the mandrel.
British Pat. No. 1,086,443 discloses a cigarette with a centrally extending cylindrical passage or with a core whose density is less than the density of the surrounding outer layer of the filler. This is supposed to slow down the rate of combustion and to reduce the temperature of tobacco smoke.